For many decades prior to the mid-1980's, conventional sandblasting using silica sand and compressed air was the preferred cleaning method for removing debris, rust, scale, coatings and corrosion from various surfaces. Conventional sandblasting was used to clean the exterior surfaces of buildings, equipment, vehicles, structures and the interior and exterior surfaces of pipe. Conventional sandblasting was inexpensive, highly effective for specific applications and provided a desirable anchor pattern for sealants and coatings to adhere. During the mid-1980's, the silica dust associated with conventional sandblasting was found to be a leading cause of Silicosis and conventional sandblasting was largely discontinued.
Although conventional sandblasting was greatly reduced, the demand for high pressure abrasive cleaning increased. Sandblasters began to experiment with their conventional sandblasting equipment by adding water to the silica sand to reduce the dust. Water/sandblasters then encountered a new problem of rusting and corroding equipment. Water/sandblasters added rust inhibitor to their water supply to combat the rust and corrosion problems, which increased their operational costs.
Water blasting, using only high pressure jets of water, has been for many years an effective means of removing some forms of debris and scale. Water blasting has many attributes, including: environmental safety, causing little damage to the surface of the object being cleaned, a relatively inexpensive blast medium and requiring little or no clean-up. However, water blasting still does not produce the abrasive forces of conventional sandblasting. Water blasting does not produce anchor patterns for sealants and coatings to adhere and water blasting alone is not practical for "hanging" applications where the operator is suspended by rope or cable above the ground, e.g. cleaning water towers, etc.
The water blast industry has, for the past several years, experimented with diverse high pressure fluid mediums and various types of soluble and insoluble abrasives for cleaning and blasting purposes. The use of abrasives in combination with high pressure fluids, is a well known material for use in water blasting applications. Insoluble abrasives such as plastic pellets and silica sand may not be environmentally safe, routinely clog the slurry nozzle, must be restricted in type and area of use and generally result in an extensive clean-up operation. Experimentation with soluble abrasives such as bicarbonate of soda in combination with a high pressure fluid medium has produced improved abrasive forces, has increased the number of water blast applications and has reduced the time spent on clean-up operations. The use of bicarbonate of soda is however, expensive, produces no anchor pattern and can not compete with the abrasive forces produced by silica sand. The water blast industry is currently experimenting with low cost, soluble abrasives which can produce an anchor patter and can effectively compete with dry silica sand. The problem lies in that both soluble abrasives and insoluble abrasives continue to create blockages in slurry nozzles with tremendous regularity, greatly reducing the productivity of high pressure fluid and abrasive mixture blasting. Therefore, a soluble or insoluble abrasive which may be perfect in every way still can not be effectively used due to the inherent problem of slurry nozzle blockages.
The blockage associated with slurry nozzles while using soluble or insoluble abrasives in combination with a high pressure fluid medium, centers on the contact between the abrasive and the residual moisture in the slurry nozzle, wherein the mixture of abrasive and moisture is not jetted from the slurry nozzle but is permitted to remain at rest in the slurry nozzle. This circumstance is common when the operator momentarily or during an extended amount of time, interrupts the water jetting operation. Contact between the abrasive and the high pressure fluid while the slurry nozzle is jetting the mixture does not generally cause blockage. During periods of interruption, residual moisture from the high pressure fluid medium is inherently present in the nozzle and unless all of the abrasive is removed from the slurry nozzle during the jetting interruption, the residual moisture reacts with the abrasive to bond the abrasive to itself and the surrounding inner nozzle surface and form a blockage. During an interruption in jetting where soluble abrasive is used, the reaction between the residual moisture and abrasive in the slurry nozzle can cause the abrasive to bond together, taking the shape of the interior passage of the slurry nozzle and completely block the nozzle. Such blockages are the most extreme and require the operator to stop the cleaning operation, disassemble the slurry nozzle apparatus, remove the blockage or repair the slurry nozzle and reassemble the slurry nozzle apparatus. Blockages rarely occur near suitable repair areas and normally occur while using the slurry nozzle at a remote location, making repair unpredictible and burdensome. Often, the blockage is so compacted and difficult to remove that the nozzle or components of the nozzle must simply be discarded and replaced.
Slurry nozzle blockages are expensive in terms of time, money and lost opportunity. Of primary importance in the present invention is to enable a slurry nozzle to be interrupted during its jetting operations while using some combination of soluble and/or insoluble abrasive and high pressure fluid, such that all of the abrasive will be removed from the nozzle and blockage normally associated with the residual moisture and abrasive will be eliminated.
It is, therefore, a feature of the present invention to provide a non-clogging high pressure slurry nozzle that prevents blockages in the slurry nozzle.
Yet another feature of the present invention is to provide a non-clogging high pressure slurry nozzle that prevents blockages in the slurry nozzle when the high pressure fluid blasting operations are interrupted.
Yet another feature of the present invention is to provide a non-clogging high pressure slurry nozzle that prevents blockages in the slurry nozzle when the high pressure fluid blasting operations are interrupted without shutting down the cleaning operation or harming the operator or surface to be cleaned.
Still another feature of the present invention is to provide a non-clogging slurry nozzle apparatus that removes abrasive material from the slurry nozzle, not requiring any affirmative action on the part of the operator.
Yet another feature of the present invention is to provide a non-clogging slurry nozzle apparatus wherein the means to remove abrasive from the nozzle includes a supply of compressed gas which forces the abrasive out of the slurry nozzle.
Another feature of the present invention is to provide a non-clogging slurry nozzle apparatus for removing abrasive from the nozzle using compressed gas which forces the abrasive out of the slurry nozzle when high pressure fluid blasting operations are interrupted.
Still another feature of the present invention is to provide a non-clogging slurry nozzle apparatus which includes a pressure actuator to control the flow of abrasive material and compressed gas through a 3-way valve to the high pressure slurry nozzle.
Yet another feature of the present invention is to provide a non-clogging slurry nozzle apparatus which includes a pressure actuator which may function under the principles of electronics, pneumatics or hydraulics.
Another feature of the present invention is to provide a method for preventing abrasive blockages in high pressure slurry nozzles.
Additional features and advantages of the invention will be set forth in part in the description which follows, and in part will become apparent from the description, or may be learned by practice of the invention. Features and advantages of the invention may be realized by means of the combinations and steps particularly pointed out in the appended claims.